Refining method and apparatus



June 20, 1950 R. H. FAsH REFINING METHOD AND APPARATUS Filed March 27,1945 NW/ EN Sw 'ji'.Eash, v NW Patented June 20, 1950 UNITED STATESPATENT OFFICE l 2 2,512,245 I REFINmG METHOD ANDAPPARATUS Ralph H. Fash,Fort Worth, Tex.

i Application March 27, 1945', Serial 585,133`

2 claims. (ci. 26o-125) This invention relates to the refining of giycneride oils for thepurpose of removing the free fatty acids and colloidalmatterv such as color particles and other colloidal impurities. Aprincipal object of the invention is to reduce the refining loss and toproduce a refined oil, or arerened oil, which is low in color andcontains less impurities than is possible using prior methods. Anotherobject of the invention is to produce a clarified refined oil. ,Anotherobject of the invention is to facilitate the centrifugal sep aration ofthe oil-soapstock mixture, produced in accordance with theI invention,by enabling such an eicess of caustic alkali to be used that a twolayersoapstock forms in the'centrifuge. Since the process involved applies inthe same manner to all animal and vegetable oils, I shall hereinafterdiscuss it, by way of example, in connection with the refining ofcottonseed oil, and it will be undern stood that thedescribed'proce'dure is typical.

This application is a continuation-impart of my application Serial No.522,135, filed February l2, 1944, now abandoned. 'A

In my Patent No. 2,342,042 of February 15, 1944, I have set forth mydiscovery that the colloidal impurities in cottonseed oil are positivelyelectrically charged and, based on this ldiscovery, I have disclosed anew refining procedure fundamentally involving the mist-mixing of theoil and refining agent. In the practice of this mist-mixing process, thesuperior results', as regards color removal and reduction in refiningloss, are attributable to the fact thatthe refining agent reacts withthe free fatty acids in the oil to form a. colloidal soapstock whoseparticles are-neg.- atively charged and, as a result of theinterspersion of these soapstock particles with the pcsitively chargedcolloidal particles in the oil, the latter are rendered electricallyneutral and will thus precipitate so as to be separable in large partwith the soapstock. In this latter connection, I have taught, in my saidpatent, that the alkaline refining agent must be used in an'amount inexcess of that theoretically required to neutralize the free fatty acidsin the oil, this for the purpose of maintaining a high pI-I up to thetime ,of separation so that the solution of electrically 2 k t jAincrease the refining loss by' occluding neutral oil" with thesoapstock.

The soapstock obtained by my mist-mixing pro#4 cedure, as described inmy said patent, ordinarily contains from to 30% neutral oil. In thecontinuous processes of refining now in use, uti'-rv lizinig liquidmixing, the soapstockv shows from 1%' vto 10% neutral oil when analyzed,but these gures do not Vrepresent the actual neutral cil con"-l tent kofthe soapstock as formed. Actually thelow neutral oil content ,shownv byanalysis is due to a large excess of caustic soda' not being entirelyconsumed before the soapstock is separated from the refined oil, and asa, result, this excess caustic soda saponies some of the neutral oil inthe soapstock, thereby lowering the neutral oil con tent in thesoapstock. Infthe process according to'my said application, the causticsoda is ordinarily used in such slight excess that very little!` iscarried vover, into vthe soapstock and, conse# quently, the neutral oilcontent of the soapstock neutralized colloidal particles in'the neutraloil oil, also reduces the formation cfa water-in-oil v. emulsion whichwouldgive a dirty oil .and would is substantially the same uponanalysisof the soapstock as when the soapstock was formed.`

Various processes have been proposed for reducing the refining lossoccasioned bythe holding of neutral oil in the separated soapstock.Chis# holm in his United States PatentNo. 1,007,642, uses sodiumsilicate to reduce the refining loss. (Unless otherwise specified, theterm sodium siln icate as used herein means lcommercial sodium silicate,commonly known asvwatcr-glass. When the term sodium silicate is usedbetween quotation marks, it refers to the compound contained in .sodiumsilicate, which latter also contains colloidal silica.) In his UnitedStates Patent No. 1,010,017, Chisholm use's sodium aluminate, so diumzincate, or sodium ferrite. 4`In using sodium silicate, Chisholm addedadded` 40 B. sodium silicate mixedwith a 16 B. caustic soda in variousproportions to the oil :being refined in `an amount substantially toIneutralize the free fatty acids, 4and besubsequentl'y added the amountof caustic soda solution normally used in the ordi nary process ofkettle refining. The refining loss obtained in some cases was lowerthan` could be obtained in the ordinarykettle process. In `other casesthere was no' reduction in the refining loss compared with' thek resultsobtained by the ordi-,- nary kettle process. The color of the refinedoil produced was, `in practically all cases, darker than that obtainedin the ordinary kettle proc-J ess. The refined oil resulting from'k theChisholm process using sodium silicate wasmuddy in appearance because ofa large amount of small particles of. soapstock 1 in `suspension; Thisin'.-l

ability to .control results in the use of the Chisholm silicate processlimited the use of the process to such an extent that its practice wasnally abandoned. The mechanism of the Chisholm process which resulted inreducing the refining loss in the case of some oils was not understoodand therefore no modification of the procedure was developed which wouldpermit of the successful application of the Chisholm process to allglyceride oils. Chisholms process using sodium aluminate, etc., wasnever practiced commercially. These later reagents were proposed merelyas being non-oil-saponifying and with no aim of reducing the retentionof neutral oil in the soap'- stock. A

The use of sodium silicate in the continuous processes of rening nowpracticed has been tried, but without success, and, in my opinion, onereason for this is because all of the caustic soda vsolution required inthe rening process has been added simultaneously with the sodiumsilicate. Thisy is in contrast to the Chisholm process according towhich, as above stated, the major portion of the caustic soda solutionwas added after the addition of the sodium silicate. In the two S.patents to Holbrook, Nos. 1,169,154 and 1,169,155, one process requiresthe addition of the sodium silicate with all of the caustic sodasolution, and in the other the ysodium silicate is added after thecaustic soda solution has been added in amount substantially suiiicientto neutralize the free .fatty acids in the oil. Neither of the Holbrookprocesses would reduce the refining loss as would the Chisholm process.This lack of success when using sodium silicate according to the twoHolbrook processes and when usingA sodium silicate in the continuousprocess of refining now in use, when compared with the success of theChisholm process on some oils, affords the basis for a denite theory ofthe mechanism of the Chisholm process, as follows:

Commercial liquid sodium silicate contains hydrous colloidal silica.When the sodium silicate, mixed with a small amount of `caustic sodasolution, is added to the crude oil being refined, in accordance withChisholms procedure, some of the sodium silicate reacts with thefreefatty acids in the :oil forming :an additional small amount ofcolloidal silica. The colloidal silica thus present adsorbs some of thecaustic soda solution subsequently added. Thedark color of the rened oilobtained is due to the retardation of saponiflcation of neutral oil byreason of the adsorption of the caustic soda solution by the colloidalsilica, and as explained in my'above-mentioned patent, in refiningprocesses involving liquid mixing, color removal occurs as a result ofthe saponification of neutral oil whereby is formed a negatively chargedcolloidal suspension which acts to electrically neutralize thepositively charged colloidal particles in the oil so that they areprecipitated. The reduction in refining loss obtained in some cases bythe Chisholm process is due to the comblned action of the colloidalsilica and sodium silicate present in the commercial liquid sodiumsilicate. Both the'colloidal silica and "sodium silicate adsorb waterthereby reducing the retention of neutral oil in the soapstock as anoilin-water emulsion. In addition, Ythe colloidal silica adsorbs causticsoda solution thereby retarding the rate of saponicationwof'the neutraloil, and there is also adsorption of the caustic solution by thesodium'silicate My theory of retarded saponfication being correct, it'would follow lthat in lthe use of my mist-mixincprocedure, which relieson the colloidal soapstock formed by the neutralization of the freefatty acids for major color removal in the rening of crude oil, retardedsaponication could be utilized for its beneiicial results while stillobtaining the necessary color removal.

In order to test the above theory, I rened a crude cottonseed oil, usingthe continuous mistmixing procedure of reiining as described in myabove-mentioned patent, with crystallized sodium meta-silicate dissolvedin an amount of caustic soda solution sufficient for rening. This sodiummeta-silicate contained no colloidal silica and, since I added itsimultaneously with all of the caustic soda solution required to rennethe free fatty acids, no appreciable amount of colloidal silicawasiormed by the action of the free fatty acids in the oil. A secondtest was made with crystallized sodium meta-silicate and colloidalsilica mixed with the amount of caustic soda solution necessary forrening. The colloidal silica was added in the form of silica jelly. Athird test was made with only silica jelly eadded to the caustic sodasolution, with the latter again in amount necessary for refining. In allof the tests, practically the same amount of excess caustic was used andall the other conditions of the tests were the same. The following arethe results of the three tests:

. Neutral Oil Test No. Loss Color in Soapstock Dr'y Basis Per Cem: PerGent 4.8 '35.0 'Y-5.5 R 6.5 4.1 35h Y-5 1 R 5.3 '4.9 35.0 Y-5.5 R 6.5

The fact is to be noted that the lowest rening loss, best color, andlowest neutral oil in the soapstock resulted 'where there was thecombined effect of the crystallized Vsodium meta-silicate and thecolloidal silica. A'laboratory test on the `same crude oil, usingcaustic soda, only, gave a rening loss of '7.0% and a color of 35;()yellow-4.9 red. Thus, in each of the three tests utilizing mistmixingthe rening loss was lless than in the laboratory test.

y In the tests utilizing mist-mixing, the amount of colloidal silicaused was about0.'03% based on the weight of the oil, the amount ofcrystallized sodium meta-'silicate was 0.25% based on the weight of theoil, and the excess caustic was .4%. The temperature of the oil fat thetime of mixing` was about F. and the temperature Iat the time of leaving'the reaction `chamber was about F.

I have added larger amounts of silica jelly to the caustic sodasolution'used inrening cottonseed oil by my mist-mixingprocess. Therefining loss and the neutraloil content of the'soapstock wasreducedibelow'that obtainable without the -useiof silica jelly. Thecolor `of the refined oil obtained was darker thanthat'produced withoutthe use of -silicajellyaswould be expected in view oftheincreasedfsaponiilcation retarding capacity. The silica `jelly.contained approximately 9% silica. 'I added20%, 30%, 40%.and 50% of thejelly, rvbased -on 'the weight ofthe caustic soda solution, to causticsoda solutions having concentrations of 32.5%, 37.1%, 43.3% and-52%`respectively so lthat the resultant` solutions had concentrations'ofabout :26% caustic soda. I found thatfasftheper'cent 4'of colloidalsilica vused increased,the .-per'centwof moisture 4in the rened .oilobtained-decreased. example,

in the above tests, the moisture content of the refined oil dropped from0.16% when using 20% silica jelly to 0.10% when using 50% silica jelly.The neutral oil content of the soapstock varied from .10.2% in therefining using 20% silica `ielly to 6.5% in the refining using 50%silica jelly.

I have successfully used as little as one-half per cent of sodiumsilicate, based on the oil being refined, added to the caustic sodasolution when refining crude cottonseed oil iby my continuousmist-mixing process, and I have found that the best results are obtainedwhen the sodium silicate has a high ratio of silica to sodium oxide, forexample, 3.9 to 1. The concentration of the caustic soda was about 26%.The refining loss was as low as that obtained using 20% to 50% silicaj`elly added to the caustic soda. I attribute the fact that I cansuccessfully use sodium silicate in the mist-mixing process ofcontinuous refining while sodium silicate when used in present dayprocesses of continuous refining cannot be successfully used, to thefact that in my process the moisture content of the soapstock is lessthan that of soapstock produced in the present day process of continuousrefining, which means that less colloidal silica and sodium silicate arerequired to reduce the formation of an oil-inwater emulsion in thesoapstock. Therefore, the amount of colloidal silica and sodiumsilicate" present in the sodium silicate plus'the amount of colloidalsilica formed in the refining operation using my mist-mixing procedureis sufcient for the purpose of reducing the amount of oil-inwateremulsion formed in the soapstock. If the amount of sodium silicaterequired to reduce appreciably the formation of the oil-in-Wateremulsion in the soapstock were used in present day continuous processes,the colloidal silica and silicate anion thus introduced would adsorbsuch a large amount of caustic soda that the refined oil produced wouldbe extremely dark.

In tests 1 and 3, hereinbefore referred to, the refining loss ispractically the same, confirming that the sodium silicate has anadsorptive capacity for caustic soda. Because of its Water adsorptivecapacity it adsorbs the caustic solution and so acts as a saponiflcationretardant. However, per unit weight it is not as effective as colloidalsilica in this respect.

The amount of the retardant (water-adsorbent) required will vary withthe available surface of the retardant. Where the retardant is incolloidal form, the greater the degree of its dispersion the less of theretardant is required to effectively reduce the rate of saponication ofthe neutral oil. Colloidal suspensions, such as chromic oxide or silicajelly, have the effective surfaces of their colloidal particles reducedon aging so that as these suspensions become. older,

more of the suspensions would be required to effectively retardsaponiflcation of neutral oil than when the suspensions are freshlymade.

In the case of compounds having only Water adsorptive anions, thesaponification-retarding and water-adsorptive effects are much less thanin the case of the colloidal suspensions referred to above and, hence,to produce an equal saponification-retarding action, much larger amountsof these compounds are needed.

In ordinary high ratio silica to sodium oxide water glass, the colloidalsilica content is approximately 50% of the total silica content. Wherefreshly made silica jelly was used in refining a low free acid oil,satisfactory results were obtained when only an amount of silica jellywas used which contained colloidal silica 'equivalent to .03% of the oilbeing refined. When using commercial water glass of the characterindicated above, .5% of the Water glass, based on the oil, was usedwhich was equivalent to using approximately .06% of colloidal silicaplus .06% of sodium silicate. The reason that more ofthe colloidalsilica contained in the Water glass was required than was necessary whenthe fresher silica jelly Was used, is due to the greater degree ofdispersion of the colloidal silica in the silica jelly than in the Waterglass. The saponicationretarding action of the water glass was due tothe combined action of the .06% colloidal silica and the .06% sodiumsilicate.

The proportions of excess caustic and sodium silicate required to beused varies with `the refining loss; the greater the refining loss thegreater the proportions of excess caustic soda and sodium silicaterequired. In the mist-mixing process of refining without the use ofsodium silicate or other Water-adsorptive agent when refining crudeglyceride oils usually found in commercial practice, an excess causticof from 0.2% to 0.3% is ordinarily sufficient. Occasionally, oils areencountered which contain an abnormal amount of colloidal material whichassists in increasing the rate of saponiiication of the neutral oilthereby more rapidly consuming the excess caustic. In order to have ahigh pH at the time of the separation of the refined oil from thesoapstock in this type of oil, an excess of caustic of more than 0.3% isrequired. l

The amount of sodium silicate, having 'a ratio of silica to sodium oxideof 3.9:1, which usually should be used in refining ordinary crudeglyceride oils is approximately one-thirteenth of the refining lossobtained by the official cup test of the American Oil Chemists Society.With an oil having a refining loss by the official cup test of 6.5%, Ihave successfully refined the oil by the continuous mist-mixing processof refining disclosed in my aforementioned patent using 0.5 of 3.9:1sodium silicate and 0.5% excess caustic soda, both based on the oilbeing refined. Where the refining loss varies from 6.5% by the officialcup test, the following formula will usually give a satisfactoryapproximation of the proportion of excess caustic soda that is to beused:

Y(excess) :O3-F??? Where a is the per cent of refining loss bytheoflicial cup test.

One of the problems in the present day practice of the continuousre-refining of glyceride oils is the prevention of the formation of atwo-layer soapstock. The extra layer consists4 of .excess causticsolution which accumulates inthe centrifuge, where the rened oil is tobe separated from the soapstock, preventing the discharge of the soap.This results in the trapping of a layer of soap between the layer ofcaustic solution against the bowl wall and the refined oil beingdischarged. When this layer of soap becomes'too great, the soapdischarges with the refined oil. This trapping of soap occurs becausethe proportion of free caustic solution to soap is large. In my saidpatent I prevent the formation of a twolayer soapstock in re-refining byusing only a slight amount of excess caustic and also by interpolating atime period between the-reaction chamber and the separating centrifuge,which results in reducing the excess caustic.

In present day practice of the continuous relining of crude glycerideoils a hard layer of soapstock accumulates on the bowl wall. Theincrease in the thickness of this layer results in decreasing theeffective diameter of the bowl thereby reducing the centrifugal forcebeing applied on the soapstock discharged. from the centrifuge. Thiscondition results in an increase in the neutral oil content of thesoapstock as a run proceeds. To overcome this condition, the present daypractice is to clean the soapstock layer from the centrifuge bowl atleast once a day. This decreases the capacity of a plant as Well .asreducing the eii'iciency of operation by reason of the gradual increasein the neutral oil content of the soapstock being discharged during arun. It is my opinion that this accumulation of soapstock on the bowlwall is due to the rough.- ness o f the wall which retards the now ofthe soapstock. This retardation results in the soap.- stock against thebowl wall being subjected to the maximum centrifugal force of the bowlfor a longer period of time than the main bulk oi the soapstock therebyreducing the neutral oil content of this retarded soapstock whichresults in increasing its specific gravity. By lining the bowl of .thecentrifuge with a smooth layer, this accumulation of soapstock can beprevented. The polishing or plating of the bowl wall would accomplishthis result but any abrasion of this rlish in the normal cleaningoperations performed when the centrifuge is shut down would initiate theformation oi this undesirable soapstock layer.

I have found that by lining the bowl with a liquid, the liquid affords aperfect surface which facilitates the movement of the soapstock from thebowl and prevents the formation of the undesirable layer of soapstock.Thus at all times, the soapstock being discharged is .subjected topractically the maximum centrifugal force of the bowl and it isY notnecessary to shut down the centrifuge to clean the bowl.

When a considerable excess of caustic solution is used, in refining bymy mist-mixing process of refining crude glyceride oils, a two-layersoapstoek is formed similar to that obtained in the re-reflning ofglyceride cils, however differing fromv the two-layer soapstock obtainedin the latter case in that the proportion of free caustic solution tosoap is small. Because of this condition, the velocity of discharge ofthe soapstock carries some of the free caustic solution whichaccumulates on the bowl wall along with the soap thus preventing thecontinued accumulation of the free caustic solution layer. Thus the bowlwall becomes lined with a liquid layer of free caustic solution overwhich the soapstock moves without touching the bowl wall, therebypreventing the formation of the undesirable soapstock layer.

If, in the absence of a saponification retardant, suflicient excesscaustic is used to produce the layer of free caustic solution, thereini-ngA loss is increased by reason of the increased saponification ofneutral oil. By using the retardant l am enabled to produce the layer offree caustic solution while controlling the saponiiication of neutraloil and holding it at a minirniun.,

The following formula gives an approximation of the excess causticrequired to produce a layer of free caustic solution on the bowl wallwhen sodium silicate is used:

8 Where ais the rening loss by the oiilcial cup'testl of the AmericanOil Chemists Society.

When a caustic soda solution is used in refining glyeride oils,particles of soap are formed. The excess caustic solution is distributedthroughout these soap particles The concentration of the causticsolution on the surface of these soap particles is reduced bysaponication of neutral oil. When a saponification retardant is notpresent, the caustic in the interior of the soap particles diffusesrapidly to the surface of the particles, the rate of diffusiondecreasing as the diierence in concentration of the caustic between thesurface of the particles and the interior decreases. Thus eventually theconcentration of the caustic on the surface of the particles arrives ata point where the soap particles will fuse together even though theconcentration of the caustic in the interior of the particles is stillsuch as would prevent coalescing if the concentration occurred on thesurface of the particles. When a saponication-retardant is present, therate of diffusion of the caustic from the interior of the soap particlesto the surface is retarded so that when coalescence occurs, theconcentration of caustic in the interior of the soap particles isgreater than is present at the time of coalescenoe when no saponicationretardant. is used. This coalescence of the soap particles when nosaponication retardant is used commences to some extent as theoil-caustic mixture is leaving the reaction chamber, as indicated by thesizeof the soap particles. When a retardant is used, the soap particlesare smaller at the time the oilcaustic-retardant mixture leaves thereaction chamber. This smaller size of the soap particles is due to thegreater concentration of caustic present at the time the mixture leavesthe reaction chamber as compared to that present when no retardant isused, and this concentration prevents the fusing of the soap particles.The greater concentration present is due to the saponication retardingaction of the water adsorptive material present and to the greaterLexcess caustic used when a retardant is present.

When suiiicient excess caustic is used, together with a retardant, whichresults in the formation of a two-layer soapstock in the refiningcentrifuge, very little agglomeration of the soap particles occursbefore the mixture enters the relining centrifuge because the largeexcess of caustic maintains too high a concentration of caustic on thesurface of the soap particles to permit major agglomeration. The majorcoalescence of the soap` particles under these conditions must occur inthe separating centrifuge after the free excess caustic solution isformed into a separate layer under the action of centrifugal force.Since the water adsorptive retardant contained in the body of the soapparticles has adsorbed to it a concentrated caustic solution, the waterin this solution is not available to form an oil-in-water emulsion withthe neutral oil.k This concentrated caustic solutionv cannot form anemulsion anymore than the concentrated solution contained in theseparated caustic solution layer in the centrifuge could form anvemulsion with the oil before being separated. This lack of ability toemulsify with the neutral oil is due to the insolubility of the soap inconcentrated caustic. solutions. Concentrated caustic solutions can 'beused to salt out soap from soap solutions in the same manner that commonsalt salts out soap from soap solutions. Therefore, the only wateravailable to form an oil-in-water solution in the soapstock from theneutral oil is that -water on the surface of the soap particles whosecaustic concentration has been reduced suficiently to permit the soapparticles to coalesce. Therefore, the soapstock has only a low neutraloil content.

In the continuous processes of refining now in use, the oil-causticmixture is usually heated to about 140 F. to obtain a break beforeseparating the refined oil from the soapstock. If the mixture wereheated to from 180 F. to 200 F. more caustic soda would be required sothat excess caustic would be present at the time the oil is separatedfrom the soapstock. This-excess caustic would result in increasing therefining loss. However, when using sodium silicate mixed with thecaustic soda solution, by reason of the adsorptive effect of thecolloidal silica and silicate anion for caustic soda, the rate ofsaponiiication of the neutral oil is retarded, in accordance with thepresent invention, so that the oilcaustic soda mixture can be heated totemperatures such as 180 F. to 200 F. prior to the separation of the oiland soapstock, without materially increased saponiiication of neutraloil by the excess caustic.

In the mist-mixing process of refining, acccrding to my said patent, anexcess of from .2% (usual) to .3% caustic is used and the mixture isheated in the reaction chamber to a temperature of about 140 F. If themixture were heated in the reaction chamber to 160 F. using the aboveamount of excess caustic, the increased rate of saponication occasionedby the use of the higher temperature would reduce the pH of the mixtureso that by the time the mixture arrived at the refining centrifuge, anincomplete separation would result. Logically, one could then reasonthat by using a lower temperature in the reaction chamber, say 120 F.,less than .2% excess caustic could be used satisfactorily. This is nottrue because at the lower temperature the soapstock formed would not besufficiently fluid to fuse together thereby causing pockets of oil to beoccluded in the soapstock. If a temperature of 160 F. or higher wereused Iit would be necessary to use more than .3% exiication retardantsuch as sodium silicate, high temperatures can be used because thesaponification retardant, by reducing the rate of Saponiiication,prevents an increase in the refining loss. At these high temperatures inthe presence of a saponication retardant, a large excess of caustic canbe used which excess is adsorbed by the saponiiication retardant, thuspermitting the reduction of the concentration of the caustic on thesurface of the soapstock which will allow the soapstock to fuse togetherreadily at the high temperatures used without the saponiflcation of alarge excess of oil because the excess caustic is adsorbed by thesaponification retardant.

As previously stated, on some oils the Chisholm process did not reducethe rening loss. These oils were oils that had a low refining lossalready, which low refining loss was due to a low neutral oil content inthe soapstock. Chisholm used the maximum amount of sodium silicate thatwould not materially affect adversely the color of his rened oil. Thismeans that the amount of sodium silicate was insuicient to reducematerially the neutral Oil content of the soapstock. If he had used`more sodium silicate (water glass), there 'would have been PreScht agreater quantity of colloidal silica and silicate anion which would have-given him a bad color by reason of the saponiiication retarding actionof these compounds. to operate at much higher temperatures beforeseparating the oil from the soapstock and thereby am able to use moresodium silicate and still obtain a satisfactory color, because thehigher temperatures permit of a more eiiicient removal of coloringmatter. I therefore am able to refine oil by my process satisfactorily.

In the continuous processes of refining now in use andin the oldkettleprocess, the oil at the beginning usually has a temperature of from F.to 90 F. The temperature at which the break occurs, namely, where theoil and soapstock separate readily, varies with the type of oil and theequipment used. In the case of kettle relining, this temperature isusually from F. to F. When sodium silicate is added to the causticsolution, the breaking temperature is from 110 F. to 120 F. In thecontinuous liquid mixing process of refining, the breaking temperatureis usually from F. to 140 F. The mechanism of the break has not beenheretofore understood in the refining industry. No explanation has beenoffered as to why the rate of heating, `for example, varies the breakingtemperature. As a result of my experience with mist-mixing refining, Ihave ascertained the mechanism which results in producing the break,

the details of which are given above.

When the caustic soda solution used in refining is added to the oilbeing refined, the resulting mixture is ordinarily called an emulsion.In my opinion, it is not an emulsion but consists of ne soapstockparticles suspended in the oil. According to my theory, on heating andagitating this suspension, the particles of soapstock agglomerate,producing the .so-called break. This agglomeration can occurindependently of temperature. With the same oil and the same amount andstrength of caustic solution, the temperature at which the break occurscan be controlled by the rate of heating and the rapidity of agitation.The break is determined by the concentrationv of the caustic sodasolution on the surface of the soapstock particles. When thisconcentration is reduced sufficiently, the soapstock particles will fusetogether causing the break. With slow heating of the oil-caustic sodamixture, the concentration of the caustic soda on the surface of thesoapstock particles is reduced to the agglomeration concentration at alower temperature than when the heating 4is rapid. Thus the sameoilcaustic mixture can be broken at 110 F. or 140 F- depending upon therate of heating, keeping the agitation constant.

The rate of saponiiication of neutral oil by the excess caustic sodaincreases with an increase in temperature. If the mixture is heated toohigh before separating the soapstock from the oil, all of the excesscaustic soda will be consumed thereby reducing the pH of the mixture.Because of this reduction of pH, more-of the electrically neutralcolloidal material will be dissolved in the oil, resulting in theformation of a water-in-oil emulsion with the soapstock as the Waterphase. This causes the soapstock to contain more neutral oil. In orderto increase the temperature at which the oil and soapstock can beseparated satisfactorily from each other, more excess caustic isrequired. The use of more excess caustic in the kettle refining processand in the continuous process utilizing liquid-mixing results inincreas- In my process, I am able glyceride oils, with caustic soda.

l 1 ing the renni'ng loss because of the saponication of neutral oil bythe excess caustic. The use of a higher temperature of the oil-causticsodamixture than is nowthe practice at the time of sepablesaponicatiomretarding agent by reason of its adsorptive capacity for thecaustic soda solution. Instead of adding the colloidal silica as such,it may be produced from silicon compounds by the reaction ofsuchcompounds, soluble in Examples of such compounds are: Methylsilicate, trimethylethoxy-silicon, hexamethoxy-disilicom and (trimethoxysilicon) (triphenoxy silicon) oxide. Othyer examples of suitablesubstances for this purpose are chromic oxide, zirconium oxide, leadperoxide, titanium dioxide, i. e., hydrous oxides which are dispersibledirectly or indirectly in caustic alkali. Hydroxides are also usable forthe same purpose Aand among these may be mentioned nickelous and cadmiumhydroxides.

Zirconium oxide, above mentioned, cannot be dispersed as a colloidalsuspension by means of caustic alkali as can, for example, chromicoxide,but it may be dispersed in a caustic alkali solution by the use of acolloid mill. This same procedure can be used in the use of nickelousand cadmium hydroxides.

It may be mentioned that various procedures .are known for obtainingcolloidal suspensions of oxides and hydroxides of metals whichordinarily.Y

would be precipitated when caustic alkali is added to solutions of saltscontaining such metals. For example, potassium tartrate used inconjunction with potassium hydroxide will form a sol of nick- !loushydroxide; cadmium hydroxide can be ob- .tained in colloidal solution byusing hot concentrated potassium hydroxide.

1 Hydrous oxides and hydroxides are, of course, water adsorptive. As hasbeen stated hereinbefore, the silicate anion of sodium silicate has aWater adsorptive capacity and a saponication retarding action. Othersalts whose anions produce similar results are the alkali aluminates,stannates, vanadates, tungstates, titanates, and zincates; in generalsalts having an anion which .is Water adsorptive. More particularly, Iuse a compound having an anion containing an element of a characterwhich is capable of forming a hydrous oxide, this capability beingmentioned by way of definition only since it may not necessarily beexercised in the refining process. However, it is my opinion that in theuse of sodium aluminate. for example, a small amount of oxide istemporarily formed and that this fugitive oxide aids in the colorreduction. The bleaching effect of clays, both acid treated anduntreated, on refined vegetable oils has been attributed to adsorptionof the color substance by hydrous aluminum silicate present in theclays. Hydrous oxides, metallic and non-metallic, are used as mordantsin dyeing where they adsorb coloring matter to form lakes. Silicon is anon-metal. The use of a hydrous metallic colloidal oxide, either addedas 'such or formed as above mentioned in .connection with sodiumaluminate, results in a better adsorpl2 tion of the coloring matter sothat the refined oil obtained will be lighter in color than thatobtained using hydrous colloidal silica.

The effect obtained by reason of the water adsorptive power of thereagents, i. e., a reduction in the neutral oil content of the soapstockis a very valuable one. The neutral oil present in soapstock occurs asan oil-in-water emulsion and also as' a water-in-oil emulsion, thesoapstock constituting the Water phase in the latter case. By reason ofthe water adsorptive power of the reagents, the formation of anoil-in-water emulsion is reduced to such a point that as little as 2%neutral oil remains in the soapstock as compred with the normal amountof from 20% to 3 The saponifcation retarding and water adsorptiv'e agentmay be introduced with the caustic solution or may be otherwiseintroduced as will be hereinafter mentioned.

In operating under the present invention using a sapcnincation-retardingagent with my mistmixing process, an excess of caustic is used beyondthat normally used in the practice of the invention as described in myaforementioned patent. By heating to 180 Eil-200 F. and keeping the oiland refining-solution mixture agitated, some of the excess causticadsorbed by the col'- loidal silica and silicate anion slowly saponilesneutral oil thereby resulting in reducing the color `of the oil byremoving some of the highly dispersed color suspensoids, this action, ofcourse, being auxiliary to that of the colloidal soapstock formed fromthe free fatty acids. This procedure differs from all other reningprocedures. In the latter, the removal of the highly dispersed colorsuspensoids occurs at relatively low temperatures and depends upon theslow saponiiication of neutral oil by reason of the low temperatures toeffect the contacting of the negative electrical charges on the soapformed with the positive electrical charges on the color suspensoidspresent in the oil. y

In my process, the adsorption of the caustic solution by the retardingagent permits the use of a high temperature to effect the sapcnicationof neutral oil which results in the removal of additional highlydispersed color suspensoids.

The temperature effect is a factor not only of the breaking temperaturebut also of the temperature at which the oil and rening agent are mixed.Ordinarily the temperature of the oil at the time it is mixed with therefining agent is from '70 F. to 90 F. If higher temperatures were usedunder present day refining practices, the refining loss would beincreased and darker colored oils would be obtained by reason of therapid saponifcation of neutral oil and the rapid agglomeration of thesoapstock thus formed. When a saponication-retarding agent is presentedin the caustic solution, higher temperatures than the above may be usedby reason of the presence of this agent. I have successfully mixed theoil and caustic solution when the oil was at a temperature of F.,subsequently heating to 180 F. to 200 F. before separating the soapstockfrom the oil. The recommended temperature to which the mixture is raisedprior to separation is, generally speaking, from about 160 F. to about200 F. By using the higher mixing temperature, there is a decrease inthe viscosity of the oil, resulting in smaller mist particles of oil inthe mist-` mixing process whereby a better Contact between the oil andthe rening agent is achieved so that ai better color is obtained than atlower temperatures.

In my aforementioned patent in the refining of crude oil, the brokenemulsion is delivered to the centrifuge Without delay in normalprocedure. lParticularly when a saponication-retardant is used, as inthe present invention, a greater time element may be introduced betweenthe reaction chamber and separating centrifuge.

Using the retardant, I have subjected the broken emulsion to agitationor turbulence for a period of a minute or two so that the following'separation gives a refined oil without` any free soapstock and withappreciable improvement in C'olor. When the oil-soapstock mixture entersthe rciining centrifuge from the reaction chamber without delay, thereare some particles of soapstock having a concentration of caustic on'their'surfaces such that the particles cannot fuse with the main bodyof the soapstock. By delaying the separation in the manner justmentioned, the'concentration of the caustic on these soapstock particlesis reduced by saponication of neutral oil thereby permitting thesoapstock particles to fuse with the main body of the soapstock. Also,some additional color particles are removed.

When reiining in accordance with the procedure given in myaforementioned patent, an 18% concentration of caustic soda is usuallysatisfactory in refining. However, when using a saponication-retardant,I have used as high as a 30% concentration of caustic soda. Usually aconcentration rof caustic soda of from 22% to 26% gives the bestresults, and I regard the practical limits as being from around 20% toaround 30%. The soapstock obtained, while hard when cold, is iluid whenhot. The iiuidity of this soapstock, even when containing less water, isgreater than the iluidity of soapstoclr not containing the retardant. Iattribute this difference in uidity to the difference in the amount ofneutral oil in the two soapstocks. In the case of the soapstock notcontaining the retardant, the emulsion formed by the neutral oilstiifens the soapstock in the same manner that the emulsion known asmayonnaise dressing is stili.

As stated above, using the retardant and subjecting the broken emulsionto agitation for a short period, I have been able to produce a rened oilcontaining substantially no free soap- `stock and this oil is otherwiseperfectly clear as it leaves the rening centrifuge. In the absence ofthe said agitation, a slight cloud forms in the oil upon cooling, thiscloud consisting of minute particles of soapstock which had beendissolved in the heated oil. While this soapstock in solution has beenpresent in the refined oil produced by customary methods of refining,its presence hasnot been recognized because of the large amount ofsoapstock suspended in the refined oil.

have discovered that by agitating the cooled oil, the minute particlesof soapstock are caused to agglomerate so that the resulting largerparticles can be removed from the oil by a clarifying centrifuge at anormal rate of through-put. The refined oil from the rening centrifugecan be continuously cooled to throw the soapstock out of solution andagitated to agglomerate the soapstock particles, and the agglomeratedsoapstock removed by a clarifying centrifuge without the necessity ofwashing and drying. The oil thus obtained contains less soap than thatproduced in the usual practice involving water washing and, of course,the process of removal is much simplified. Onereason for the betterresult is that when the washing procedure is used, the washwaterretained in the Washed oil has to be evaporated with the resultthat the soap which was dissolved in the water becomes dissolved in theoil.

When the oil-soapstock mixture is subjected to proper agitation inadvance of the refining centr'ifuge the cloud above mentioned will notform upon cooling, and the refined oil can be run directly to aclarifying centrifuge for the removal of any free soapstock. As a matterof fact, there is so little free soapstock, if any, in the oil havingthe 'refining centifuge that the subsequent clarication step couldordinarily be omitted, but to be on the safe side I ordinarily includethe step.

The agitation prior to separation can be very effectively accomplishedusing a Votator which is a heat-transferring and agitating devicemanufactured by the Girdler Corporation of Louisville, Kentucky. In theVotator I, for best results, maintain the temperature of theoil-soapstock mixture and may even raise the temperature to any pointdesired. However, it is simpler to impart the desired temperature to themixture entirely in the reaction chamber.

A probable explanation of the mechanism of the action of the use of theVotator between the reaction chamber and the reiining centrifuge toprevent the formation of a, cloud in the refined oil after the oil isseparated from the soapstock is as follows:

At the temperatures used in rening glyceride oils, they have the abilityto dissolve some water, which water in the refining operation has soapdissolved in it. Upon cooling the oil, some of this water is thrown outof solution as a cloud in the oil. This cloud is in reality a suspensionof droplets of emulsion in the oil by reason of the emulsifying actionof the soap in this water deposited from the oil in cooling. Thesedroplets ci emulsion do not coalesce readily. This is the conditionwhich prevails when a Votator is not used between the reaction chamberand the refining centrifuge and the reiined oil discharged from thereiining centrifuge is cooled.

When a Votator is used between the reaction chamber and the reningcentrifuge the water in solution in the oil is removed from the oil bythe adsorptive effect ci the water adsorptive retardant present in thesoapstock. Since the Water is only slightly soluble in the oil and theWater adsorptive material has an aiiinity for Water, the Votator bybringing the oil in intimate contact with the soapstock causes the oilto become dry. This dried oil on being separated from the soapstock`will not have a cloud formed in it when cooled because of the absence 0fwater.

t is obvious, therefore, 'that the described agitation of theoil-soapstock mixture in advance of the reiining centrifuge, when usinga saponi.- iication retardant in accordance with the present invention,brings about a number of very important results.

In the refining procedures hereinabove considered, the original reiiningof crude oil has been principally in mind. However, the presentinvention extends also to re-reiining or retreatment for the purpose ofcolor removal just as in my aforementioned patent. According to thatpatent, a very slight excess of the caustic solution is usediure-refining and the same slight excess is usable when asaponification-retardant is used in accordance with the presentinvention. In other words, the excess over that theoretically requiredasians 15 to neutralize the free fatty acids in the oil may be of theorder of .05% or less with consumption of the excess to such an extentthat upon separation only a trace will remain for the purpose ofmaintaining the pH.

The hydrous oxides and hydroxides hereinbefore mentioned function alsoas color adsorbents, as has been pointed out. In re-reiining, theseagents may be viewed from another standpoint, namely, that of theirability to electrically neutralize colloidal particles which escapedneutralization during original rening and are still electrically chargedin the reined oil.

Under this contemplation, there may be added to the reiined oil a highlydispersed negatively charged colloidal suspension made, for example, byadding approximately 1.4 parts of a 50% s0- lution of sodium hydroxide(or an equivalent quantity of potassium hydroxide) to approximatelyparts of a 4% solution of chromium acetate. As a result of the additionof the sodium hydroxide to the solution of the chromium salt, there isformed a highly dispersed colloidal suspension of chromic oxide andwhen, as in the example just given, a suicient quantity of sodiumhydroxide is used, the colloid will be negatively charged.

In the case, for example, of a 5.5% free fatty acid oil which has beenpreliminarily refined, a colloidal suspension of chromic oxide preparedin the manner described above may be added in the approximate proportionof 2% parts 4of the colloidal suspension to 1GO parts of the oil. Thecolloidal suspension is intimately mixed with the oil, preferably bymist-mixing. The mixing may be carried out at room or highertemperatures and the emulsion then broken with subsequent separation ofthe soapstock from the oil with the pH maintained up to separation.

By .re-refining in this manner, I have obtained a rened oil with asubstantially lower color and with substantially less refining loss thancan be obtained by prior practices. For example, starting with acottonseed oil having a free fatty acid content of 5.5%, I have obtainedby means of preliminary refining and subsequent treatment with a highlydispersed negative colloids, an oil having a color of 35 yellow-10 redwith a reiining loss of 14%. Starting with the same oil and using thestandard procedure now practiced in the art, an oil having a color of 35yellow-18 red was produced with a 17% rening loss. It would be necessaryto re-rene the 18 red oil at least twice to lower the color to red and,in so doing, the total rening loss would reach a figure betweenapproximately 21% and 23%.

Whether, in re-reiining, a hydrous compound is used in the aspect ofelectrical neutralization or in the aspect ofsaponiiloation-retardation, both properties of the compound are, ofcourse, exercised. In the aspect of electrical neutralization and in thecase, for example, of chromium oxide, in forming the oxide, it is onlynecessary to add sufficient caustic to the chromium salt to insure theformation of a negatively charged suspension and to insure the presenceof at least a trace of the caustic at the time of separation, andseparation may follow immediately after mixing. In the aspect ofsaponiiication-retardation, the caustic is used in amount somewhat inexcess of that theoretically required for the neutralization of the freefatty acids and a delay is introduced to permit saponication :of theneutral oil for the purpose of color removal. Of course, in this latter16 situation, the oxide is also exerting its e'ect'oi electricalneutralization and in both cases the water and color adsorptive effectsof the oxide are realized.

In the original mist-mixing refining of crude oil, I ordinarily selectthe hydrous materials with sole reference to their capacity for wateradsorption, this in view of the fact that the colloidal soapstocknecessarily formed can be relied on for the neutralization of thecharged particles.

Prior to my recognition of the effect of caustic adsorption by hydrousoxides and hydroxides, I had refined crude oil using such a substance onthe basis of its capacity for electrical neutralization in conjunctionwith a sufficient amount of refining agent to neutralize the free fattyacids. As an example, 21/2 parts of the colloidal suspension of chromicoxide described above, together with 0.4 part of 50% sodium hydroxidewere added to 100 parts of a 0.8% free fatty acid oil. After mixing andseparating, an oil having a. color of 35 yellow-4.5 red was obtainedwith a refining loss of 4%. It will be seen that in the example justgiven the ratio of chromic oxide to the oil by weight was about the sameas that of the colloidal silica in tests Nos. l, 2 and 3 hereinbeforementioned.

It will be understood that the ratio of alkali to salt in the colloidalsuspension may be varied through a wide range, it being only necessaryto have any amount of alkali greater than that which is theoreticallynecessary to react with the salt. The concentrations of the salt andalkali are likewise variable. Where the colloidal suspension is added tothe oil, the amount which is used may vary but it has been found that ifthe concentration of the salt is increased, it is necessary to add agreater amount of the colloidal suspension to the oil. This isapparently due to a lessening of the dispersion of the col'- loidalsuspension upon an increase in the concentration of the salt.

While the colloidal suspension may be formed before mixing it with theoil, from a practical standpoint, I prefer to form it in the oil. Forexample, the solution of chromium salt and caustic alkali may be addedseparately to the oil, with agitation and formation of the colloidalsuspension in the oil. Or, and still better, the metallic compound maybe directly dissolved in the oil, and then the alkaline agent may beadded to the solution with intimate mixture therewith. In carrying. outthe last-mentioned procedure, the solution and the alkaline agent arepreferably mist-mixed.

As examples of suitable metallic compounds soluble in animal andvegetable oils, the following may be given by way of example: trimethylaluminum, diethyl aluminum, tridodecyl aluminum, tetramethyl tin,tetraethyl tin; in general, organic metallic compounds having thegeneral formula RM where R represents the ethyl or methyl group and Mrepresents the metal group; organic metal compounds of the chelate type,and inorganic compounds such as stannic chloride, titaniumtetrachloride, and aluminum chloride. Examples of silicon compoundssoluble in glyceride oils which will react with caustic alkali to formhydrous colloidal silica are: methyl silicate, trimethyl-ethoxysilicon,hexamethoxy-disilicon, and (trimethoxy silicon) (triphenoxy silicon)oxide. In general, any compound soluble in the oil which will react vI7`-=with'analkaline 'agent to form-'the oxide for-hydroxide of theelement may be used.

As an example of procedure, I added 0.343% of `stannic'chloride to dryrened cottonseed oil having a color of 35.0 yelloiv, 9.7 red, and afreeacid -content of 0.3% and subsequently treated the oil 'withagitation with 1.46% of' 20% caustic soda solution', heating the mixtureto 140'F- There- `sultant 'oil had a color ef '35.0 yellow, 4.9 red. Inv"general, the amount of alkali agent mixed with vvr'ei'ined oilcontaining a saltin solution is prefsolved in the oil, With thoroughdistribution;

Water is intimately admixecl, as lby mist-mixing. The electricallycharged coloring matter in the oil vis not removable to any appreciableextent hy adsorption, and consequently, when this is the matf-ter, orsome of it, desired to be removed, theb 'negatively charged colloidalsuspension should be used.l Such a suspension has also the 'capacity ofrendering the originally charged color particles l"electrically neutraland hence susceptible, as well 4jas'the originally neutral'matter, ofadsorption.

, stated at the outset, the present invention 4`is* 'applicable in therefining of glyceride oils for :the purpose of removing free fatty acidsand/or v"colloidal impurities. As vegetable oils otherthan cottonseedsusceptible of treatment in accord- 'ance with the invention, I` maymention peanut foil, soyalbean cil, palm kernel oil, linseedV oil,coconut oil, and sesame oil; and as animal oils, tallow, whale oil,menhaden oil, shark oil. These :species are mentioned merely .by Way ofexample In the accompanyingdrawing; I have shown apparatus vsuitablefor'the ypractice 'ofthe present invention using mist-mixing.

Referring to the drawing, reference numeral I "designates a tank for theoil to be refined or re-L frened and, as shown, it isv equipped withatemperature-conditioning coil 2 and with an agitator 3dr`iven from abelt 4. The coil maybe used to heat the oil, ifv such 'heatingis-desired, and the agitator is useful, forexample, 4when it is' desiredl"tomix some substance intimately Withthe oil.'

y*A pipe 5 leads from the bottom' of tank l adapted to deliver the oilto a centrifugal atomiz- *ing and mixing head i3 mounted in a closedreaction chamber M and driven from a beltV The heat exchanger II maybeused inplace oi the coil 2 to heat the oil to any desired'temperature.The coil 2 is ordinarily used to heat the oil *as an aid to the mixingof a treating .substance therewith.

" Reference numeral vI6 designates a tank for y'-thefrening agent and ishere shown as equipped with a temperatureconditioning coili'll and withvanagitator I8 driven from a belt I9. Aipipeil rleads ffrom the ybottom'oi tankvl 6 through avalve 2l to a variable delivery pump -22AWlfiichzissontrolled by a hand wheel 23 on the panel 9; The output ofthe pump goes through a pipe l2li-:to a metering devicel 25 and thencethrough apipe $36 to a delivery means at the head I3. -Means fordelivering the oil and reiining agent to the head andthe headconstruction are fully describe-din my aforementioned patent and also inmy Patent No; 2,341,536 of February l5, i944, so that repetition hereisbelieved to be unnecessary. Moreover, it will he understood that thecentrifugal atomizing and mixing head is referred toV herein merely asthe best means knowny to me for-producing homogeneous mist-mixtures.

' reactionchamher lll is laterally jacleted throughout for thecirculation of a temperature'- conditioning lwhich, in thepresent'case,1` will be a heating medium lead lto the jacket-from l'anysuitable source through a pipe'l and leaving through an outlet pipeChamber le has a bottom outlet pipell which discharges into upwardlyopen receiver 3i! having a bottomv outlet in connection with aV pump 3lWhose outlet is in connection With a pipeu32 leading to a valve 3d. Inone adjustment voi the valve, the output of pump 3l is sent' directly toa pipe dll which delivers to a reiining centrifuge 35. ln anotheradjustment of valve 33 the pump output is delivered to an agitating 'anddelaying device 35S and thence to the pipe Slltvhichidelivers to thecentrifuge. The'device 36 may also he equipped fortemperature-conditioning and may conveniently and effectively beconstituted by the Votator alhove mentioned.

Centriiuge '35 has an oil outlet vpipe orsp'out 3'? through whichreiined oil can :be delivered to a receiver 38, or hy manipulation ci"`avvalvef-39 the output can be diverted to a pipe 4S. Thereceiver 38 hasa bottom outlet connection with a pump il whose outlet leads to a valve`llzgto-'be directed hy the latter either to a pipe 43 or to a heattransfer and agitatingy device' Alllydesirably a Votatorz The outlet oi"thedevice' 4l! s in connection by means o2 a'pipe (35, in Wllicirisiriterposed a vaive (le, with a valve 'lll 'by' means. of

which pipe @it can 4beplaced in connection with a delivery pipe'f for aclarifying Icentrifuge'.

Pipe t3 leads through a'valve 5d to the top lof a tank 5i equipped witha heat exchanging coil 52 and an agitatorv 53 driven from a belt 54.Tank 5I has a bottom outlet in connection with-valve lll through a pipede and, when valve'l'! is appropriately adjusted, tank 5I can drain intothe clarifying centrifuge throughtlie' pipe 55. `The clarifyingcentrifuge has an oil.` delivery pipe-"or spout '56.

*In the practice of the invention, tank Icontains crude oil and tank E6contains-the 'caustic solution and, in preferred practice, aWater-adsorptive substance Which is distributed throughout the causticsolution bythe agitator im. If

vmixing is to occur at room' temperature,- coils 2 and il and the heatexchanger ll are inactive. However, if mixing is to occur at an elevatedtemperature, as I prefer to do and am enabled to'fdo when using asaponiiication rctardanuithefoil is heated to the desiredtemperatureusing either the coil 2 or the heat exchanger I hor-both; andthe refining agent may also be -heatedffrom the coil il. rlhe preheatingis such,r for example-as to bring the mixing temperaturetoI from 110"F.to 169 F.

Valves t and .El being opened and pumps 1 and '22 operating, the oil andreiining solution canfbe -delivered to the head ISf in exactly theydesired proportions by observing the flow meters l2 and :25 andadjusting the delivery of the pumps by means of the hand wheels 8 and23. The substances delivered to the head I3 are instantaneously reducedto mists, i. e. aerosols, mixed, and projected radially as a homogeneousmist-mixture. The term mist-mixing as used herein covers the formationof separate mists or aerosols before mixing, or the merging of thesubstances as liquids prior to mixing as mists or aerosols. If merged,in the case of reactants the point of mergence should not be so far inadvance of the head I3' as to permit major reaction of the substances tooccur while they are still in liquid form since otherwise thedisadvantages inherent in liquid-mixing refining will begin to appear.Mist-mixing applies to the above described procedure wherein the causticalkali and water-adsorptive agent are mixed as liquids and the liquidmixture is then mist-mixed with the oil. There is an ultimatemist-mixture of all of the substances, although some of them werepreliminarily mixed as liquids. By a mist or "aerosoY I mean dispersionsof minute particles which are of approximately colloidal dimensions asin a mist or fog. I do not limit the terms to include only those systemswhich will remain in dispersion for a long period of time, but, on thecontrary, I use the term to describe the character of the dispersion atthe time it is formed. I am not concerned with the permanency orstability of the mists or aerosols since the mixing thereof can beaccomplished in` a fraction of a second.

If mixing has occurred at room temperature, the collecting walls of thechamber 4 need be heated only sufficiently so that the mist whichcollects thereon as a liquid emulsion will have an emulsion breakingtemperature imparted thereto as it flows downwardly as a nlm or thinlayer on the walls. The imparted temperature may be in the neighborhoodof 140 F. but preferably will be higher, for example, 180 F. If mixinghas occurred at a temperature as high as 160 F., chamber I4 need beheated only suiiiciently to substantially maintain the mixingtemperature, which is also a breaking temperature. However, even if amixing temperature as high as 160 F.

has been used, chamber |4 is preferably heated so as to further raisethe temperature above the breaking temperature, for example, to form 160F. to 200 F., the optimum range being from about 180 F. to about 200 F.and the optimum `temperature being 180 F. or thereabout. Al-

though mixing may have occurred at a temperature above the breakingtemperature, the socalled emulsion nevertheless forms because, the

`heat being not extreme, and the saponifcation retarding agent beingpresent, the caustic is not immediately consumed.

It is my opinion that the neutralization of the free fatty acids iscompleted before the mistmixture reaches the walls of the reactionchamber. There is some saponiiication of neutral oil by the excesscaustic during flow down the chamber walls and to the outlet pipe 29 andup to the time of separation.

With pipe 29 delivering to the receiver 30 and the pump 3| in operation,the broken emulsion can be sent directly to the refining centrifuge 35,when valve 33 is appropriately set. In this case, it frequently occursthat free soapstock will be observed in the discharge. As above stated,this free soapstock can be entirely eliminated, or nearly so, and thecolor somewhat improved if a greater time lag is interposed between thereaction chamber and centrifuge, particularly, if during this period,the oil-soapstock mixture is agitated, and when agitation is applied, nocloud will for-m in the rened oil upon cooling. Hence, I prefer to putthe mixture through the device 36 and this device may also supply heatso as to maintain the temperature of the mixture. I have successfullyused a coil in place of the Votaton except as regards the elimination ofthe cloud, the time of flow through the coil being between one and twominutes.

When the Votator 35 or like agitating device is used, the reiined oilcan leave the refining centrifuge by way of pipe 40 to any desireddestination, or it may go directly to the clarifying centrifuge,by-passing both device 44 and tank 50. To accomplish the latter effect,a pipe 51 connects pipe A3 just below valve 50 with pipe 45 just abovevalve 45 and includes a valve 5B adjacent pipe 43 and a valve 59adjacent pipe 45. By adjusting valve 42 so as to connect pump 4| withpipe 43, closing valve 50, opening valves 58 and 59, closing valve 45,and adjusting valve 41 to connect pipes 45 and 48, the pump will deliverdirectly to the clarifying centrifuge.

In some cases, it may be desired to get the broken emulsion to therefining centrifuge with the least possible delay and agitation so as toprevent re-emulsication and in that case the pump 3| can be omitted orby-passed or the reaction chamber outlet pipe can be made to deliver bygravity directly to the centrifuge.

If clarication is to be carried outvby prior methods, the output of therefining centrifuge can be directed through pipe 40 to any desired pointof storage or treatment. However, cloud removal may be effected by theclarifying centrifuge when the oil is cooled and agitated infad- Vancethereof.

To this end, valve 33 is adjusted toby-pass "Votator 36 and the refiningcentrifuge ismade to deliver to the receiver 38. Valves 42 and 41 beingproperly set, the rened oil will pass through the device 44 wherein itis cooled to a temperature preferably below F. and subjected toagitation so that the soapstock which was dissolved in the heated oil isthrown out of solution and the soapstock particles coalesce so as to bereadily separable from the oil by the clarifying centrifuge 49 at anormal rate of through-put.

Or, without changing the setting of valve 41, by adjusting valve 42, soas to connect pump 4| with pipe 43, tank 5| can be filled. The oil inthe tank may be permitted to cool normally or cooling may be acceleratedby ycirculating a cooling medium through the coil 52. After the oil hascooled suiciently so that the dissolved soapstock is thrown fout ofsolution, the agitator 53 -is operated to cause the coalescence of theparticles and thereafter valve 41 may be adjusted so as to connect pipes48 and 55 for delivery of the oilto the clarifying centrifuge. In thisiconnectiornI may mention that a series of three tanks, such as aredisclosed in my above-mentioned Patent No. 2,342,042, may be used withthe arrangement such that while one tank is emptying, another is beingfilled and a third tank is standing full.

In the above description of the operation of.

the system shown in the drawing, the adsorbent was said to be mixed withthe caustic alkali in the tank |6. However, the additive may b eintroduced independently of the caustic, if desired,

and by the use of a multi-fluid nozzle such as is disclosed in myaforementioned Patent No. 2,341,536.

It will be seen that the illustrated apparatus is capable of carryingout all procedures which have been discussed herein and with variationin accordance with the results desired. However, l believe I have madeit clear that the method of the present invention is by no means limitedwith respect to apparatus. The invention extends to all procedures andapparatus within the denitions of the following claims.

I claim:

1. The process' of refining a crude glyceride oil, which comprisesmist-mixing the oil with a water-adsorptive agent selected from thegroup Kconsisting of sodium silicate, colloidal silica, and mixturesthereof, and with a caustic alkali solution whose concentration issubstantially within the range of 20% to 30% and which acts toneutralize the free fatty acids present in the oil to form soapstock,collecting the mist mixture on a surface from which it flows as a.mixture of liquid oil and soapstock, imparting to the oilsoapstockmixture a temperature substantially within the range of 160 to 200 F.,agitating the mixture to bring the oil into intimate contact with theWater-adsorptive agent present in the soapstock While maintaining thetemperature of the mixture against substantial decline, and separatingthe soapstock from the oil, the caustic alkali being used in an amountin such excess of that necessary to neutralize the free fatty acids thatsome of the caustic alkali is present at the time of separation and saidagent being used in an amount effective to substantially reduce theneutral oil retained by the soapstock and to retard the saponifcation ofthe neutral oil.

2. The process according to claim 1 wherein the soapstock is separatedfrom the oil in a centrifuge and the excess caustic is present at thetime of separation so that a two-layer soapstock forms in thecentrifuge.

RALPH H. FASI-I.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 342,692 Grant May 25, 1886596,411 Lugo Dec. 28, 1897 1,169,154 Holbrook Jan. 25, 1916 1,447,898Schlossstein Mar. 6, 1923 2,337,041 Giles Dec. 21, 1943 FOREIGN PATENTSNumber Country Date 537,682 Great Britain July 2, 1941

1. THE PROCESS OF REFINING A CRUDE GLYCERIDE OIL, WHICH COMPRISESMIST-MIXING THE OIL WITH A WATER-ADSORPTIVE AGENT SELECTED FROM THEGROUP CONSISTING OF "SODIUM SILICATE," COLLOIDAL SILICA, AND MIXTURESTHEREOF, AND WITH A CAUSTIC ALKALI SOLUTION WHOSE CONCENTRATION ISSUBSTANTIALLY WITHIN THE RANGE OF 20% TO 30% AND WHICH ACTS TONEUTRALIZE THE FREE FATTY ACIDS PRESENT IN THE OIL TO FORM SOAPSTOCK,COLLECTING THE MIST MIXTURE ON A SURFACE FROM WHICH IT FLOWS AS AMIXTURE OF LIQUID OIL AND SOAPSTICK, IMPARTING TO THE OILSOAPSTOCKMIXTURE A TEMPERATURE SUBSTANTIALLY WITHIN THE RANGE OF 160* TO 200*F.,AGITATING THE MIXTURE TO BRING THE OIL INTO INTIMATE CONTACT WITH THEWATER-ADSORPTIVE AGENT PRESENT IN THE SOAPSTOCK WHILE MAINTAINING THETEMPERATURE OF THE MIXTURE AGAINST SUBSTANTIAL DECLINE, AND SEPARATINGTHE SOAPSTOCK FROM THE OIL, THE CAUSTIC ALKALI BEING USED IN AN AMOUNTIN SUCH EXCESS OF THAT NECESSARY TO NEUTRALIZE THE FREE FATTY ACIDS THATSOME OF THE CAUSTIC ALKALI IS PRESENT AT THE TIME OF SEPARATION AND SAIDAGENT BEING USED IN AN AMOUNT EFFECTIVE TO SUBSTANTIALLY REDUCE THENEUTRAL OIL RETAINED BY THE SOAPSTOCK AND TO RETARD THE SAPONIFICATIONOF THE NEUTRAL OIL.